1. Field of the Invention
The present invention relates generally to optical switch devices, and more particularly to an optical switch device that deflects light signals input from multiple input ports using multiple defection parts on a channel-by-channel basis, and outputs the deflected light signals from corresponding output ports.
2. Description of the Related Art
Wavelength division multiplexing (WDM) is an effective technique for constituting a large-capacity optical communications network, and WDM traffic has been exploding these days with the explosive spread of the Internet.
A common optical cross-connect (OXC) system as a backbone optical network according to WDM is formed of multiple optical signal exchangers interconnected by optical fibers. When a WDM light signal is input to the optical signal exchanger through an optical fiber, the optical signal exchanger switches the route of the light signal wavelength by wavelength, and can transmit light signals in the same route in the form of a WDM light signal.
According to such an optical cross-connect system, if an optical fiber forming a communications route fails, it is possible to restore the system at high speed by immediately performing automatic bypassing to a backup optical fiber or the optical fiber of another route. Further, it is also possible to edit optical paths wavelength by wavelength.
In a MEMS (Micro Electro Mechanical Systems) optical switch, concern about reliability is greatest for a MEMS mirror that mechanically operates among the components of the optical switch. It is necessary to detect failure of the MEMS mirror in order to increase the reliability of an optical communications system.
In the conventional MEMS optical switch, light sources are connected to all the input ports of an optical switch through corresponding couplers, and abnormality is detected by monitoring the output levels of all the output ports of the optical switch as described in Patent Document 1.
Further, Patent Document 2 discloses the technique of detecting an abnormality in a scanner from the difference between the oscillation frequency of a movable piece and an applied resonance frequency, the difference in phase between the scanning position of the movable piece and an applied AC (alternating current) voltage, or reduction in the maximum scanning angle of the movable piece.
[Patent Document 1] Japanese Laid-Open Patent Application No. 2004-48187
[Patent Document 2] Japanese Laid-Open Patent Application No. 6-123845
However, according to the conventional MEMS optical switch of Patent Document 1, the light sources of test light are connected to all the input ports and the output levels of all the output ports are monitored, thereby detecting abnormality. Accordingly, the number of test light sources increases so as to cause the problem of an increase in cost and device size. Further, the number of optical components such as light sources and monitors increases, thus causing the problem of reduced reliability of the switch.